Control circuit for an electric machine having an electronic commutator

ABSTRACT

A control circuit is disclosed for a converter fed electric machine in which thyristors, arranged in separate channels, are used as an electronic commutator. A rotor position transmitter in conjunction with three Hall effect generators produces pulsed signals mutually displaced 120 electrical degrees from each other. These signals, in combination with their inverse Hall signals, are used with logic circuitry to control the conduction period of the thyristors. The logic circuitry for each thyristor is composed of a first and second control circuit. The first control circuit comprising an addressing stage or NOR gate provides a pulse signal to control the conduction of the thyristor to insure maximum torque on starting. The second control circuit provides a thyristor control signal displaceable in time and the displacement of which is related to the desired displacement angle between the armature and the excitation field under the prevailing operating conditions. These two control signals are provided as input signals to a selective output circuit which controls the thyristor conduction period in response to the first occurring signal from either of the two control circuits.

United States Patent [1 1 Poppinger et al.

[ CONTROL CIRCUIT FOR AN ELECTRIC MACHINE HAVING AN ELECTRONICCOMMUTA'IOR [75] Inventors: Herbert Poppinger,

Erlangen-Sieglitzhof; Klaus Hiiber, Erlangen, both of Germany [73]Assignee: Siemens Aktiengesellschait, Munich,

Germany [22] Filed: Aug. 17, 1972 [2]] Appl. No.: 281,493

[30] Foreign Application Priority Data Aug. 20, 1971 Germany P 21 41622.8

[52] US. Cl. 318/254 [51] Int. Cl. H02k 29/02 [58] Field of Search318/138, 254

[56] References Cited UNITED STATES PATENTS 3,663,877 5/1972 Clark318/138 3,696,277 10/1972 Liska 3,483,457 12/1969 Fertig...

3,483,458 12/1969 Kirk 3,678,358 7/1972 Kolatorowicz 318/254 PrimaryExaminerBernard A. Gilheany Assistant ExaminerThomas LangerAttorneyI-lugh A. Chapin et al.

[57] ABSTRACT A control circuit is disclosed for a converter fedelectric machine in which thyristors, arranged in separate channels, areused as an electronic commutator. A rotor position transmitter inconjunction with three Hall effect generators produces pulsed signalsmutually displaced 120 electrical degrees from each other. Thesesignals, in combination with their inverse Hall signals, are used withlogic circuitry to control the conduction period of the thyristors. Thelogic circuitry for each thyristor is composed of a first and secondcontrol circuit. The first control circuit comprising an addressingstage or NOR gate provides a pulse signal to control the conduction ofthe thyristor to insure maximum torque on starting. The second controlcircuit provides a thyristor control signal displaceable in time and thedisplacement of which is related to the desired displacement anglebetween the armature and the excitation field under the prevailingoperating conditions. These two control signals are provided as inputsignals to a selective output circuit which controls the thyristorconduction period in response to the first occurring signal from eitherof the two control circuits.

9 Claims, 3 Drawing Figures 3 Q Q Q I i B r i U T Tr U1 Hy a e si U lHZW Ill E: II +g 4-5 fi I]? l (L now H2 MW H n em.

U 1: u i v nL PATENTEDDED 1 1 I975 SHEET 2 BF 2 HHH H I I I CONTROLCIRCUIT FOR AN ELECTRIC MACHINE HAVING AN ELECTRONIC COMMUTATORBACKGROUND OF THE INVENTION 1. Field of the Invention This invention isconcerned with a control circuit for an electric machine having anelectronic commutator. More particularly it is concerned with a controlcircuit for an electric machine having an electronic commutator in whicha d-c link and a rotor-position dependent transmitter, whose Hallsignals and corresponding inverse Hall signals, are used to form controlsignals for the individual thyristors of the commutator.

It is an object of the invention to start a converter-fed motor withmaximum torque, and, for speeds different from zero, to displace theangle between the armature and the excitation field, automatically andcontinuously, from ill 90 to smaller angles, and to match the angle r1190 to the prevailing operating conditions, regardless of the type ofconverter, so that optimum power factor and efficiency occur over theentire speed range of the converter-fed motor.

2. Summary of the Invention According to the invention, the problem issolved by controlling the individual thyristors by either an addressingcircuit, dependent upon Hall signals, to generate fixed-control pulses,or a distributor stage dependent on both simultaneously occurring Hallsignals and on pulses, which are displaceable in time as a function offrequency and are common to each thyristor pair in a channel. Thus thefirst occurring output signal of either the addressing circuit or thedistributor stage, determines the conduction state of the thyristor.

BRIEF DESCRIPTION OF THE DRAWINGS Further details of the invention willbe explained more fully with reference to an example of an embodimentschematically shown in the drawings, in which:

FIG. 1 illustrates a converter-fed three-phase motor with d-c link;

FIG. 2 illustrates the time relationship of all control signals; and

FIG. 3 illustrates a control circuit according to the invention for twoseries-connected channels of the stator. I

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 shows a simplifiedpresentation of a selfcontrolled converter-fed motor M having a d-c linkL,,. The converter consists of six thyristors pl to p6 in a bridgecircuit, the firing signals of which are derived depending upon therotor position, in the known manner, from a rotor position transmitter(not shown). The magnetic wheel of the transmitter, secured on the motorshaft,'upon rotation, causes three Hall effect generators, mutuallydisplaced by 120 electrical degrees and arranged in stationary relationat the motor housing, to transmit Hall signals H1, H2, H3.

Each of the Hall signals has a signal length of 180 electrical degreesand is electrically displaced relative to each other by 120. The inverseor reciprocal Hall signals HI, H2, H3 of corresponding nature as shownin FIG. 2 are also transmitted.

By linkig two Hall signals, six fixed control pulses U1 to U6 areobtained for the control of thyistors p1 to p6 of the converter. Forexample by appropriate circuitry a control pulse U1 can be produced bythe simultaneous occurrence of a pos itive Hall signal H1 and a positiveinverse Hall signal H3. Further through appropriate correlation of thefixed control pulses with the individual thyristors, the angle betweenthe armature field and the excitation field can be adjusted to 11: forthe starting of the motor M and the development of its maximum torque.In operation, however, the motor can not be run with i]: 90,particularly with commutation by the machine voltage. This means that inorder for the drive to operate at all, in each case the fixed controlpulses must be determined and advanced against the direction of rotationby a displacement angle to be determined in each case.

The angle ill is chosen in machine-commutated converter-fed motors insuch a manner that they operate capacitatively in order to make therequired reactive commutation power available. On the other hand, inconverter-fed motors, with forced commutation, the angle :1: is to bematched to the operating conditions in such a manner that they operatewith optimum power factor.

For shifting the fixed control pulses U1 to U6 according to FIG. 2, asawtooth signal 1', is generated which is synchronized by the fixed Hallsignals H2, H3, H2, H3 and linearly changes with time. This sawtoothsignal is compared with a comparison signal i,,, proportional to thedisplacement angle, to permit the continuous changing of thedisplacement angle d) between its limits. In order to make thedisplacement angle 4) independent of both the speed of rotation and thefrequency of the converter-fed motor, when the comparison signal ismaintained constant, the slope of the sawtooth signal is thereforecontrolled as a function of frequency.

FIG. 3 shows, in a simplified manner, part of the circuit for generatingthe fixed control pulses and the pulses displaced by the displacementangle shown by dashed lines for the cooperatig thyristors p1 and p4 oftwo channels I and IV, displaced by electrical degrees. A similarsituation also applies to the other channels for controlling the otherthyristor pairs p2, p5 and p3, p6, respectively.

At standstill, when no displaced pulses are yet generated, the fixedcontrol pulses are formed by so-called addressing circuits 1, 2 (NORgates) and fed to the input of the output stage 3 or 4, respectively. Inthe example shown the output stage 3 of channel I conducts and drivesthe associated thyristor pl through a matching stage, not shown, onlywhen the Hall signals H1 and H3, fed to the addressing circuit l, areboth simultaneously positive. This condition exists during the timeinterval a l to a 3 (FIG. 2). The thyristor associated with channel IV,p4, conducts through the corresponding, separate addressing circuit 2for simultaneous positive Hall signal H1 and H3 during the time intervala 4 to a 6.

For displacing the fixed control pulses at a speed of the motor Mdifferent from zero, a sawtooth signal is generated in the followingmanner:

The output voltage U, (FIG. 2) of an integrator 6 is used as thesawtooth generator through a synchronizing stage 5 connected to oneinput of integrator 6. Synchronizing stage 5 consists of two NOR gatesinfluenced respectively by the Hall signals H2, H3 and the inverse Hallsignals H2, H3. The integral will always have its highest negative valueif in the intervals a l to a 2 and a 4 t( a 5, (FIG. 2) either theinverse Hall signals H2 and H3 or the Hall signals H2 and H3 aresimultaneously positive.

During the remainder of the period the integration capacitor C ofintegrator 6, having a switchable parallel path associated with it forthe purpose of limiting the voltage, is linearly discharged by a speedorfrequencyproportional current i generated in a current source 7connected with the input of the integrator 6. The output voltage U,changes in the positive direction, until at the time a l or a 4, duringthe synchronization time, the above-mentioned recharging of thecapacitor C begins. The output voltage U, produces a current i, which iscompared at the input of the flipflop 8, with reference (comparison)current i, which is proportional to the displacement angle The output offlipflop 8 is connected to both distributor stages 9 and 10. The outputvoltage U K of the flipflop 8, fed to the distributor stages 9, 10, isnegative for i,, 2 i,, and jumps to its positive maximum value at i, si,, (FIG. 2). Displaced pulses with twice the firing frequency of thethyristor are therefore fed tothe distributor stages 9 and 10 of the twochannels I and IV, which operate with a mutual displacement of 180electrical degrees.

The distributor stage 9 is further influenced by the Hall signals H2 andH3, and the distributor stage 10 by their inverse Hall signals H2 andH3. Thus, the output of the distributor stage 9, is fed to the outputstage 3, for instance, can become positive only if a displaced pulse isto be generated, and only when the output voltage U,, of the flipflop 8and the Hall signals H2 and H3 are all simultaneously positive. In thatcase, the thyristor pl of channel I is driven into conduction, althoughno signal is then present through the addressing circuit 1. Therefore,the time of firing thyristor pl is determined by the earlier existingpositive signal of either the addressing circuit 1 or the distributorstage 9. A similar situation is true regarding the thyristor p4 ofchannel IV with respect to the signals of addressing circuit 2 and thedistributor stage 10. In this manner, a continuous transition from fixedcontrol pulses to displaced pulses (dashed in FIG. 2) is obtainedwithout any separate switching means whatsoever.

In the six-pulse converter circuit shown in FIG. 1, another two pulsegenerator stage of the kind shown in FIG. 3 must be provided forchannels II and V as well as III and VI for the thyristors p2, p5 andp3, p6, respectively. In order to assure a pulse duration of 120electrical degrees for the displaced pulses, the three respective outputstages 3 and 4 of one half of the bridge are interlocked with thyristorsp1, p2, p3 and p4, p5, p6. For this the cathode of one diode n1 or n4,of the output stages 3 and 4 of channel I and IV is connected with theinput, e.g., the collector of a transistor of a subsequently conductingoutput stage of channel II AND V (not shown) so that the correspondingtransistor Tr of the output stage 3 and 4 of channel I and IV is cut offwhen the output stage of channel II or IV, is controlled intoconduction, and the pulse for the associated thyristor, pl or p4, isthereby terminated. In a similar manner the output stages of the otherchannels are also interlinked.

Because the displaced pulses for the thyristors which are operative for180 electrical degrees, for instance, p1 and p4, are derived from thesame sawtooth signal, they have exactly the same pulse length, so thatthe motor winding does not carry an undesired d-c component.

The slope of the sawtooth signal U, is obtained from the relation U /At= i,,/C N i,/A t N n/C, as i, is proportional to n.

However, as A i,,/A t= i,,/( /m )N n/C, one has dmN i (wC/n), and henceqbN i because n is proportional to The relation between the comparisoncurrent i and the displacement angle :1) is linear and independent offrequency. This also applies analogously to the displacement voltageU,,, which depends on the type of the converter commutation. Thedisplacement voltage U, is changed, for instance, as a function of theload current Jg (FIG. 1) in the case of machine commutation withconstant machine excitation, or as a function of the speed in the caseof forced commutation with constant machine excitation (matching of theconstant reversal frequency of the commutation circuits to the variablemachine frequency).

If the displacement angle 11) is increased beyond f, the motor voltage UM (FIG. I) is reversed while the direction of the load current J gremains the same, so that the machine is now braked as a generator(twoquadrant operation), without the need for a separate reversingconverter.

In the case where four-quadrant operation is required of the machine,two Hall signal pairs are interchanged by a separate, external switch(not shown), for example, H1 with H2, H1 with H2, because of thesequence of the channels I, II, III and IV, V, VI due to the interlockat standtill, so that the control can work correspondingly in the otherdirection of rotation.

What is claimed is:

l. A control circuit for an electric machine having a direct currentlink to an electronic commutator, the electronic commutator comprised ofa plurality of control thyristors connected in a plurality of channels,each channel having at least two thyristors, said machine further havinga rotor position transmitter for generating a plurality of positive andinverse Hall voltage signals, the positive Hall signals comprisingvoltage pulses having a periodicity of 180 electrical degrees and amutual displacement from each other of electrical degrees, the controlcircuit comprising:

means to generate a pulse signal having a phase angle related to apredetermined displacement angle between armature and excitation fieldof the machine,

a first control circuit means for producing a first thyristor controloutput signal, the input to said circuit means comprising twopredetermined positive and inverse Hall voltage signals, mutuallydisplaced from each other by 60 electrical degrees, said circuit meansproducing a control signal for starting the motor, the control outputsignal occurring only during the period when the two Hall input signalsare positive,

a second control circuit means for producing a second thyristor controloutput signal, said circuit means having an input comprising two otherpredetermined positive and inverse Hall voltage signals, mutuallydisplaced from each other by 60 electrical degrees, and said pulsesignal said second control circuit means producing a control outputsignal only during the period when all three inputs are positive, and

an output circuit means connected to a thyristor in said commutator,said output stage having two inputs, one from said first control circuitmeans and the other from said second control circuit means, said outputmeans controlling the conduction of said thyristor in response to thefirst occurring signal from either of said control means so that thethyristor conducts to maintain a predetermined displacement anglebetween the armature and the excitation field of the machine.

2. A control circuit for an electric machine as in claim 1 wherein saidelectronic commutator comprises six thyristors connected in threechannels and wherein each thyristor has a control circuit to maintainthe predetermined displacement angle between the armature and theexcitation field of the machine.

3. A control circuit for an electric machine, having a direct currentlink to an electronic commutator, the electronic commutator comprised ofa plurality of control thyristors coupled to armature windings in themachine, said machine further having means for generating a plurality ofHall signals at least equal to the number of armature windings in themachine and indicative of the rotor position with respect to thewindings and means for generating the inverse of said Hall signals,comprising for each of the control thyristors:

a first control circuit means responsive to at least one of said Hallsignals and inverse Hall signals to produce a first output signal whichis in a fixed phase relationship to the rotor;

means to generate apulse signal representing a predetermined phase anglebetween the armature and excitation field of the motor;

a second control circuit means responsive to at least another of saidHall signals and said inverse Hall signals and further responsive tosaid pulse signal representing said predetermined phase angle, saidsecond control circuit means providing a second output signal only whenboth said at least another of said Hall signals and inverse Hall signalsand said pulse signal are present; and

an output circuit means having said first and second output signals asinputs and providing an output to turn on its associated thyristor wheneither of said output signals is present.

4. A control circuit for an electric machine as in clai 3 in which thepredetermined displacement angle pulse signal is produced as an outputof a flipflop circuit whose input signal is the sum of a signalproportional to the displacement angle and a controlled frequencysawtooth signal.

5. A control circuit for an electric machine as in claim 4 in which thecontrolled frequency sawtooth sig nal is produced as an output of anintegrator whose first input is a positive directly coupled outputsignal from a synchonrization stage, having two NOR gates, the inputs tothe first of which are two predetermined Hall voltage signals and theinputs to the other of which are the inverse of the first twopredetermined Hall voltage signals, and whose second input is aresistively coupled negative signal proportional to the speed of theelectric machine.

6. A control circuit for an electric machine as in claim 5 in which thesecond input to the integrator is a signal proportional to the frequencyof the machine.

7. A control circuit for an electric machine as in claim 4 furthercomprising an interlocking circuit between each output stage of therespective conducting thyristor and the previously conducting thyristorso that the output of each output stage of a thyristor control circuitis connected to the input of the output stage of the thyristorpreviously controlled into conduction.

8. A control circuit for an electric machine as in claim 7 in which theinterlocking circuit is comprised of a diode.

9. A control circuit for an electric machine as in claim 3 in which thefirst control circuit means comprises a first NOR gate, the secondcontrol circuit comprises a second NOR gate, and the output stage iscomprised of a diode controlled transistor stage having an output onlyupon the conduction of the diode.

UNITED STATES PATENT OFFICE GERTIFIQATE 0F (IORRECTION Patent No. 3,77 9Dated December 11, 1973 F ORM PO-105O (10-69) I fl Herbert Ponpinsaerand Klaus Hiibner It is certified that error appears in theabove-identified patent and that said Letters Patent are herebycorrected as shown below:

In column 1, line 66 change "linkig to --linkin g In column 3, line 28,change "stage 9 is fed to" to a --stage .9, fed to" In column 3, line57, change "channel II AND V to 7 ---channel 11 and V-- In column A,line 6 change, "Ug/At i /c N i /At N n/C" "to u /At i /C' i /A tn/C-- Incolumn A, line 7, change "A1 /At 1 N n/C, one has+ N i c/n), and enceMWibecause...

to: -Ai AA i/(bby'n/c, onehas 43A) iv (QC/n), and

hence wi because.

In column 6, line 6 (claim 4) change in 'clai 3" to --i n claim 3--Signed and sealed this 24th day of December 1974.

(SEAL) Attest:

McCOY M. GIBSON JR. C. MARSHALL DANN Attesting Officer Commissioner ofPatents USCOMM'DC 60376-P59 V U.S. GOVERNMENT PRINTING OFFICE: 1989O366-J34,

UNITED STATES PATENT OFFICE CERTIFICATE OF (:ORRECTEQN Patent No.3,778,691 Dated December 11, 1973 Inv nt fl Herbert Ponpinezer and KlausHfibner It is certified that error appears in, the above-identifiedpatent and that said Letters Patent are hereby corrected as shown below:

In column 1, line 66, change "linklg to --linkin g In column 3, line 28,change "stage 9 is fed to" to ---stage 9, fed to In column 3, line 57,change "channel 11 AND V" to --channel 11 and V-- In column L, line 6change "U /A t si /C N i /At N n/C" to --U /At i /C' i /A t n/C columnline 7, change "A5. /At 5. N n/C,

one has+ N i pC/n), and ence N i because.

to: Ai KAt i /(b b)r-'n/C, one has +N iv *(QC/n), and

hence i because.

In column 6, line 6 (claim 4) change "in 'clai 3" to --in claim 3--Signed and sealed this 24th day of December 1974.

(SEAL) Attest:

McCOY M. GIBSON JR. C. MARSHALL DANN Attesting Officer Commissioner ofPatents F ORM PO-IOSO (10-69) uscomm-oc eosve-pes [1.5. GOVERNMENTPRINTING OFFICE: 1989 O355334,

1. A control circuit for an electric machine having a direct currentlink to an electronic commutator, the electronic commutator comprised ofa plurality of control thyristors connected in a plurality of channels,each channel having at least two thyristors, said machine further havinga rotor position transmitter for generating a plurality of positive andinverse Hall voltage signals, the positive Hall signals comprisingvoltage pulses having a periodicity of 180 electrical degrees and amutual displacement from each other of 120 electrical degrees, thecontrol circuit comprising: means to generate a pulse signal having aphase angle related to a predetermined displacement angle betweenarmature and excitation field of the machine, a first control circuitmeans for producing a first thyristor control output signal, the inputto said circuit means comprising two predetermined positive and inverseHall voltage signals, mutually displaced from each other by 60electrical degrees, said circuit means producing a control signal forstarting the motor, the control output signal occurring only during theperiod when the two Hall input signals are positive, a second controlcircuit means for producing a second thyristor control output signal,said circuit means having an input comprising two other predeterminedpositive and inverse Hall voltage signals, mutually displaced from eachother by 60 electrical degrees, and said pulse signal said secondcontrol circuit means producing a control output signal only during theperiod when all three inputs are positive, and an output circuit meansconnected to a thyristor in said commutator, said output stage havingtwo inputs, one from said first control circuit means and the other fromsaid second control circuit means, said output means controlling theconduction of said thyristor in response to the first occurring signalfrom either of said control means so that the thyristor conducts tomaintain a predetermined displacement angle between the armature and theexcitation field of the machine.
 2. A control circuit for an electricmachine as in claim 1 wherein said electronic commutator comprises sixthyristors connected in three channels and wherein each thyristor has acontrol circuit to maintain the predetermined displacement angle betweenthe armature and the excitation field of the machine.
 3. A controlcircuit for an electric machine, having a direct current link to anelectronic commutator, the electronic commutator comprised of aplurality of control thyristors coupled to armature windings in themachine, said machine further having means for generating a plurality ofHall signals at least equal to the number of armature windings in themachine and indicative of the rotor position with respect to thewindings and means for generating the inverse of said Hall signals,comprising for each of the control thyristors: a first control circuitmeans responsive to at least one of said Hall signals and inverse Hallsignals to produce a first output signal which is in a fixed phaserelationship to the rotor; means to generate a pulse signal representinga predetermined phase angle between the armature and excitation field ofthe motor; a second control circuit means responsive to at least anotherof said Hall signals and said inverse Hall signals and furtherresponsive to said pulse signal representing said predetermined phaseangle, said second control circuit means providing a second outputsignal only when both said at least another of said Hall signals andinverse Hall signals and said pulse signal are present; and an outputcircuit means having said first and second output signals as inputs andproviding an output to turn on its associated thyristor when either ofsaid output signals is present.
 4. A control circuit for an electricmachine as in clai 3 in which the predetermined displacement angle pulsesignal is produced as an output of a flipflop circuit whose input signalis the sum of a signal proportional to the displacement angle and acontrolled frequency sawtooth signal.
 5. A control circuit for anelectric machine as in claim 4 in which the controlled frequencysawtooth signal is produced as an output of an integrator whose firstinput is a positive directly coupled output signal from asynchonrization stage, having two NOR gates, the inputs to the first ofwhich are two predetermined Hall voltage signals and the inputs to theother of which are the inverse of the first two predetermined Hallvoltage signals, and whose second input is a resistively couplednegative signal proportional to the speed of the electric machine.
 6. Acontrol circuit for an electric machine as in claim 5 in which thesecond input to the integrator is a signal proportional to the frequencyof the machine.
 7. A control circuit for an electric machine as in claim4 further comprising an interlocking circuit between each output stageof the respective conducting thyristor and the previously conductingthyristor so that the output of each output stage of a thyristor controlcircuit is connected to the input of the output stage of the thyristorpreviously controlled into conduction.
 8. A control circuit for anelectric machine as in claim 7 in which the interlocking circuit iscomprised of a diode.
 9. A control circuit for an electric machine as inclaim 3 in which the first control circuit means comprises a first NORgate, the second control circuit comprises a second NOR gate, and theoutput stage is comprised of a diode controlled transistor stage havingan output only upon the conduction of the diode.